1. Field of the Invention
This invention relates generally to inflatable vehicular safety restraint assemblies such as airbag installations for automotive vehicles and, more particularly, to inflatable vehicular safety restraint assemblies that discharge or provide inflation gas to an airbag cushion in a cross-car manner.
2. Discussion of Related Art
It is well known to protect a vehicle occupant by means of safety restraint systems which self-actuate from an undeployed or static state to a deployed state without the need for intervention by the operator, i.e., “passive restraint systems.” Such systems commonly contain or include an inflatable vehicle occupant restraint or element, such as in the form of a cushion or bag, commonly referred to as an “airbag cushion.” In practice, such airbag cushions are typically designed to inflate or expand with gas when the vehicle encounters a sudden deceleration, such as in the event of a collision. Such airbag cushion(s) may desirably deploy into one or more locations within the vehicle between the occupant and certain parts of the vehicle interior, such as the doors, steering wheel, dashboard or the like, to prevent or avoid the occupant from forcibly striking such parts of the vehicle interior.
Various types or forms of such passive restraint assemblies have been developed or tailored to provide desired vehicle occupant protection based on either or both the position or placement of the occupant within the vehicle and the direction or nature of the vehicle collision. Automotive passenger side airbag installations generally incorporate an airbag module assembly having an inflator device within a module housing or canister and an inflatable airbag cushion adapted to inflate out a side of the module housing. In one currently used passenger side airbag module assembly configuration the inflatable airbag cushion is adapted to inflate out a top side of the module canister, often referred to as a “top mounted” airbag cushion. Such a module assembly is installed in the dashboard of the automobile close to the windshield. Upon activation, the inflator device releases inflation gas which inflates the airbag cushion. The top mounted airbag cushion initially inflates toward the windshield and then rapidly rolls down the dashboard in a direction toward the passenger.
One common form of inflator device stores or contains a pyrotechnic, propellant or other type of gas generant material which, upon actuation of the device, ignites or reacts to rapidly form or produce large volumes of inflation gas used to inflate an associated airbag cushion to protect vehicle occupants.
As will be appreciated, the manufacture of such reactant gas generant material-containing inflator devices necessitate the taking of special care, not only during the manufacturing process but also during subsequent storage, handling, shipping and transportation, for example, to ensure avoidance of inadvertent ignition or reaction of the gas generant material contained within the inflator device. Moreover, in view of the widespread use of such inflator devices, large numbers of gas generant material-containing inflator devices are routinely shipped and transported, such as to various vehicle assembly plants.
The risk of inadvertent reaction of a gas generant material-containing inflator device is generally very small in view of currently applied safety practices.
In the past, gas generant material-containing inflator devices have raised a concern, such as in the event of a fire during the shipping or storage of the devices, that the gas generant material contained within the device would ignite or react to produce or result in the release of gases which could cause a condition of high thrust such that an unrestrained inflator can form or act as a projectile that may create a risk to personnel standing nearby or those trying to put out the fire.
As a result of such possible risk, the United States Department of Transportation requires that inflator devices be subjected to a bonfire test wherein an inflator device even when placed directly in a fire cannot become a projectile upon ignition of the stored gas generant material.
To satisfy such test requirements, inflator manufacturers have developed methods and techniques to balance the gases exiting or discharging from an inflator device to create a “thrust neutral” or “zero thrust” inflator.
One approach has been to design an inflator device to have a plurality of gas discharge holes or openings radially disposed around the circumference of the inflator device. This technique is relatively easy and simple to employ in passenger side inflators and other applications such as where the inflator device is stored in a module housing assembly. For example, many current passenger side airbag module assemblies incorporate inflator devices having inflation gas exit areas, from the inflator device itself or, if used, an associated or included diffuser element, which are dispersed about the inflator device or the associated diffuser to provide or result in 360° gas diffusion to create a device that is thrust neutral.
Moreover, in the past, inertia welding has been a typical or standard welding technique applied to or with inflator device production. Unfortunately, inertia welding typically results in random placement of the discharge openings of the inflator device or, if present, the associated diffuser. The random placement of the discharge openings results in inflators, such as typical disk type inflators, having or providing 360° gas diffusion to ensure thrust neutrality.
One such disk type inflator device is shown in FIG. 1 and generally designated by the reference numeral 20. The inflator device 20 has a generally flat cylindrical shape, sometimes referred to as a “disk” shape, with a plurality of gas discharge holes or openings 22 radially disposed around the circumference of the inflator device. As shown in FIG. 1, the inflator device 20 may include or have joined thereto an attachment collar flange or bracket 24 such as having a plurality of fastener openings 26 disposed thereabout such as to permit the inflator device to be appropriately fastened into place in an associated module housing.
While such 360° gas diffusion can desirably serve to result in a device that is thrust neutral, the use of inflator devices that produce or result in such inflation gas diffusion has frequently necessitated other modification to module assemblies. For example, module assemblies have required the inclusion of rings or deflectors such as to redirect the inflation gas in order to appropriately fill the airbag cushion to provide desired protection to the vehicle occupant.
In practice, such 360° gas diffusion creates at least two additional major concerns for module development. Firstly, the 360° gas diffusion can create severe stresses on the car-forward & car-rearward walls of the passenger airbag module housing. Secondly, the 360° gas diffusion can cause or result severe deformations such that can damage instrument panel components and the cover door over the passenger module housing.
Efforts to address such concerns have included modifying the module housing such as through the inclusion of significant features such as to stiffen the car-forward & car-rearward walls of the passenger airbag module housing such as to prevent this deformation (such deformation being commonly referred to as “bell-mouthing”).
Reference is now made to FIGS. 2-5 which illustrate a prior art airbag module assembly 30 including the prior art inflator device 20.
The airbag module assembly 30 includes a generally rectangular module housing 32 having a first pair of opposed walls including a car-forward wall or edge 34 and an opposed car-rearward wall or edge 36 and a second pair of opposed walls including first side wall 40 and a second side wall 42.
The housing 32 also includes a base wall 44 such as having an opening 46 therethrough for placement of the inflator device 20.
The airbag module assembly 30 further includes an appropriately shaped, sized and positioned deflector ring 50 such as forming or including a vertical deflector wall 52 extending about the inflator device 20 such that gas thrust neutrally exiting from the inflator device 20 through the plurality of gas discharge holes or openings 22 is directed vertically out of the housing (such as represented by the arrows 60) such as to appropriately inflate an associated airbag cushion.
As will be appreciated, the need for the inclusion of such added structural features, such as to deflect or redirect the inflation gas and/or to strengthen or modify the module housing such as to prevent this bell-mouthing deformation can significantly increase product cost as well as undesirably increase the weight and size of the module assembly.
Further, such turning of inflation gas to come out of the housing can act to create a column of gas that may undesirably be directly directed towards a vehicle occupant. This can be particularly significant in the event of an out-of-position (OOP) vehicle occupant, such as where an OOP vehicle occupant may be in close proximity to the airbag cushion. In such a situation, if not otherwise addressed, such an assembly operation can create an undesirable risk of injury to an OOP vehicle occupant. Thus, such assembly operation has been commonly addressed via inclusion, either in or with the module and/or otherwise in or by the safety restraint system, of additional countermeasures to minimize and avoid such risk. These countermeasures may, for example, involve a second turning of the inflation gas, such as turn the inflation gas after exiting the module housing.
The inclusion of such countermeasures can also have an undesirable impact on assembly and system size and weight as well as cost.
Thus there is a need and a demand for module assemblies and techniques that can desirably remove the need for turning the inflation gas multiple times during a crash event, yet still be able to satisfy inflator level thrust neutrality requirements for shipping. Further, there is a need and a demand for module assemblies and techniques that reduce the risk of inducing occupant injury in OOP conditions. Yet further, there is a need and a demand for module assemblies and techniques that remove the need for module level content to achieve inflation gas turning and to make the product more efficient. Yet still further, there is a need and a demand for module assemblies and techniques that reduce the need for the use of techniques and inclusion of module features such as added module housing stiffening features and thus can act to improve product features such as package size, weight, etc.